1. Field of the Invention
The present invention relates to a method for supplying works contained in a pallet and an apparatus therefor, adapted for use in various working machines such as an automatic working machine or an automatic assembling machine.
2. Related Background Art
A pallet supply apparatus, for supplying pallets to various machines such as an automatic working or assembling machine, is in general precisely positioned with respect to such working machine, and is usually constructed as a fixed unit in order to ensure the assembling precision by an assembling robot.
Also in the working or assembling lines in the manufacturing factory, the locations of the working or assembling machines may be varied depending on the size of such machines or according to various limitations in the facility. In such case, the articles to be worked, or works, are contained in pallets and such pallets are transported by an automatic cart or manually on a pallet supply apparatus.
FIG. 5 is a lateral view of a conventional pallet supply apparatus, wherein unrepresented elevator means in a supply apparatus 122 can move between an upper position and a lower position, thereby supporting and transporting pallets 1.
Above an equipment 170 such as a working or assembling machine, there is provided a robot unit 150 having a robot hand 150h which moves the works from the pallet 1 to an assembling jig pallet 180 as indicated by arrows. Between the supply apparatus 122 and the equipment 170 there are provided a pallet-introducing conveyor 120 with a stopper 124 and a pallet-discharging conveyor 119 with a stopper 123, both of which are partly supported by a conveyor support 121. There is further provided an elevator 125 for vertically moving the pallets 1.
The pallet supply operation in the above-explained conventional structure is conducted in the following manner. The supply apparatus 122, composed for example of an automatic cart, is moved perpendicularly to the plane of drawing to a predetermined position, and a lower pallet 1 therein is moved to the position of the stopper 124 of the pallet-introducing conveyor 120. Then the pallet 1 is moved, by the release of the stopper 124, to the position of the elevator 125, and is subsequently elevated to the illustrated position, at which the works in the pallet are moved to the jig pallet 180 by the robot hand 150h as indicated by arrows. When the pallet is emptied, the elevator 125 descends to the height of the conveyor 119 and the pallet 1 is moved until the right end thereof impinges on the stopper 123. Subsequently the stopper 123 is released to move the pallet 1 to the upper position of the supply apparatus 122.
Consequently the stacked pallets 1 are positioned in succession in the working range of the robot hand 150h.
Also the present applicant already proposed a pallet supply apparatus, as a U.S. patent application Ser. No. 493,437 filed Mar. 14, 1990, abandoned and refiled on Feb. 6, 1992 as Ser. No. 07/830,488, now U.S. Pat No. 5,190,434, which dispenses with the fixed mechanism associated with the pallet supply apparatus, thereby reducing the cost thereof and also dispensing with the pallet loading/unloading operation on the pallet supply apparatus at each pallet supply.
However, the conventional pallet supply apparatus as shown in FIG. 5, requiring associated fixed mechanisms as explained above, has been associated with the drawbacks that the apparatus is inevitably expensive, that pallet loading/unloading operation is indispensable on the pallet supply apparatus at each pallet supply, and that the robot hand may collide with the stacked pallets 1 positioned within the working range of said robot hand.
On the other hand, the pallet supply apparatus previously proposed by the present applicant has been associated with a low operation rate because the continuous operation of a certain equipment (robot unit) has to be interrupted, as the pallet supply apparatus has to be moved from the loading position to said equipment at the replacement of an emptied pallet with another pallet filled with the works.